Howling detection device, howling suppressing device and method of detecting howling

A howling detection device capable of detecting the occurrence of howling with a higher degree of accuracy is provided. The howling detection device includes a signal level calculating unit calculating, from the input signal, an input signal level being the signal level of an input signal at each given time, a level fluctuation estimated value calculating unit calculating, from the input signal level, a level fluctuation estimated value being a value gradually increasing or decreasing by a given amount with time, a threshold value calculating unit calculating, from the level fluctuation estimated value, a level threshold value changing in accordance with the level fluctuation estimated value, and a howling determination unit which determines that howling occurs in an input signal under the condition that the input signal level being higher than the level threshold value continues for a given time.